This invention relates to the art of electrochemical cells, and more particularly to a new and improved wound element electrode assembly for use in lithium batteries for delivering high current pulses.
One area of use of the present invention is a battery for operating an implantable cardiac defibrillator, although the principles of the present invention can be variously applied. The purpose of the implantable defibrillator is to prevent sudden death from lethal arrhythmia, and in operation the device continuously monitors the heart rate of the patient, is able to recognize ventricular fibrillation, and subsequently delivers a high energy shock to defibrillate the heart. In order to power this device, implantable high rate batteries have been developed which have the ability to deliver a current pulse and rapidly recover the open circuit voltage.
Examples of batteries having high capacity, low self-discharge and good pulsing behavior at all levels are shown and described in U.S. Pat. Nos. 4,830,940 and 5,549,717. Manufacture of the cell stack assembly in the battery of U.S. Pat. No. 4,830,940 includes, briefly, folding the anode to form a serpentine-like structure, placing individual cathode plates between the folds of the anode structure, and then making electrical connection including welding operations to individual leads of each of the plurality of cathode plates.
U.S. Pat. No. 5,549,717 is directed improved high rate battery which reduces the time required to manufacture the cell stack assembly while maintaining the requisite safety and reliability standards in operation. The combination of elongated anode and cathode electrodes is wound using a mandrel to form an anode-cathode sub-assembly having a jellyroll type configuration and shaped so that the resulting sub-assembly has a substantially rectangular configuration for assembly into a cell casing of prismatic shape.
In the manufacture of a wound anode-cathode sub-assembly using a mandrel, it is important to insure that removal of the mandrel from the completed sub-assembly does not cause any damage which ultimately could adversely affect the operation of the electrochemical cell in which the anode-cathode sub-assembly ultimately is used.
It would, therefore, be highly desirable to provide a new and improved wound anode-cathode sub-assembly and method of making the same which maintains the requisite safety and reliability standards in the operation of an electrochemical cell in which the sub-assembly is used.